The present invention relates to a continuously variable transmission means for transmitting torque from a driving pulley to a driven pulley, both the driving and driven pulleys have contact surface cross-sections which are V-shaped.
A continuously variable transmission (CVT) comprises a V-belt extending between a driving and a driven pulley, the ratio capable of being varied (ratio being defined as the RPM or speed ratio between the driven and driving pulleys), by adjusting the size of a V-shaped opening(s) in one or both of the pulleys or by varying the pressure which forces the belt into the opening(s). Thus, the position of the belt on the pulleys and the effective diameter of the pulleys can be varied, which makes it possible to continuously vary the ratio between the driven pulley and the driving pulley.
Prior techniques for forming a belt member for a continuously variable transmission include using a predetermined number of metallic hoops upon which longitudinally shiftable V-shaped block members are mounted, the V-shaped block members are linked together and extend around the total circumference of the hoops. The driving force from the driving pulley is then transmitted to the driven pulley by a movement of the V-shaped block members. The block members transmit the driving force to adjacent blocks toward the driven pulley. Thus, the block members gradually transmit the force of the driving pulley to the driven pulley, at points where the block members are in contact with the driven pulley.
A known continuously variable transmission has block members which engage with adjacent block member and move in a straight relationship with each other when in a straight extension area between the driving and driven pulleys. However, when the block members are displaced from the straight extension area and contact a point around a peripheral portion of one of the pulleys, a block member contacts an adjacent block member at a position located at an inner radial point, rather than at a position where the endless carrier engages with the block members. Hence, the rotating radius of the endless carrier is larger than the rotating radius of the block members, where the block members have a rotating radius defined as the radius of the combined circular arc formed between block members adjacently contacting each other. The block members can move relative to each other because the block members contact adjacent block members at different points. This sliding movement results in friction between the endless carrier and the block members and therefore consumes some part of the driving force from the driving pulleys as friction. This impairs the efficiency of the continuously variable transmission.